Morphological abnormalities in frogs from a rice-growing region in NSW, Australia, with investigations into pesticide exposure

Three frog species were surveyed in rice bays of the Coleambally Irrigation Area (CIA) NSW during the rice-growing season. A total external morphological abnormality index of 7% was observed. No conclusive evidence was found of unnaturally high rates of intersex, gonadal maldevelopment or unbalanced sex ratios in any species. Rice bay surface waters differed significantly in mean pesticide concentration of atrazine and metolachlor on farms growing rice and corn compared to farms growing rice only. However, the similar abnormality indices observed in recent metamorphs emerging from these two farm types provided no evidence to suggest a link between larval exposure to the measured pesticides and developmental malformations.